Men's Health: Low sperm count linked to mother's high-beef diet during pregnancy

Researchers believe they've uncovered a new explanation for why some men have low sperm counts: Their mothers ate too much beef during pregnancy.

Dr. Shanna Swan of the University of Rochester in New York State and her colleagues studied 387 expectant fathers, some of whom had seen a doctor about possible infertility prior to their partner's pregnancy. The researchers also interviewed the men's mothers about their diet while pregnant.

The more beef a mother ate during pregnancy, the lower her son's sperm count. For example, men whose mothers ate more than seven beef meals per week while pregnant had sperm concentrations more than 24 per cent lower than those of men whose mothers ate seven or fewer beef meals per week.

Nearly 18 per cent of the sons of high beef consumers were considered less than normally fertile, compared with less than six per cent of the sons of women who ate less beef. And nearly twice as many had seen a doctor for possible infertility before their partner became pregnant.

Swan notes that the men's own meat consumption was not associated with semen quality -- the association was only with the mother's diet. She says this is likely because the testicles are more sensitive to their surroundings in the womb than after birth.

One possible explanation for the results is that natural and synthetic hormones fed to beef cattle may be present in the resulting meat products and influence fetal development when eaten by the mother. A second possibility is that these results may be linked to persistent pollutants that accumulate in fat, such as pesticides and dioxin.

Whatever the explanation, Swan cautions it is too early to make recommendations based on this research. "This is not definitive," she says. "If it makes you feel good to do something, you could decrease your beef consumption or eat organic beef. At this point that's not something that we can actually say will rule out the problem."

And she stresses that protein is an essential part of the diet. "I don't want women to take this and say, 'Oh my God, I can't eat any more beef,' and then suddenly not get enough protein in their pregnancy."